Theoretical insights into 2D siloxene as a promising anode material for lithium-ion batteries

Abstract

Two-dimensional siloxene (Si₆O₃H₆) has garnered significant interest as an anode material for lithium-ion batteries (LIBs) in the development of energy storage devices, delivering an experimental reversible capacity of 2300 mAh g⁻¹. To complement the experimental efforts and to gain an in-depth theoretical understanding of the mechanisms behind its diverse electrochemical performance, we systematically explored several influencing electrochemical factors, including Li-adsorption behavior and binding energy, kinetic analysis, voltage profiles, and specific capacity at the atomic level using first-principles calculations. The 2D siloxene monolayer (OH–Si–H) exhibits high structural and thermal stability, excellent electronic conductivity, strong lithium storage capability (−3.25 eV), a high theoretical capacity of 1129.18 mAh g⁻¹ – up to three times greater than that of commonly used graphite – and a low average open-circuit voltage of 0.66 V. More importantly, the Li-adsorbed siloxene monolayer maintains a high stiffness of 201.23 N m⁻¹, demonstrating its mechanical robustness under electrochemical cycling. Li⁺ migration on the siloxene surface is confirmed to be fast on the lower side, owing to a low barrier energy of about 0.34 eV and the corresponding diffusion coefficient of 1.95 × 10⁻⁶ cm² s⁻¹. With these unique properties, 2D siloxene can serve as an excellent anode material for LIBs.